7-8 is best
I assume you're joking. That. is. massive.
Idk, personally speaking I find lengh as an indicator of pleasure much overrated. At a certain lengh it just gets uncomfortable during sex and it hurts when it hits the cervix, so a little shorter might actually be better for everybody involved. I realize not all women are built the same and vaginal lengh in relation to cervix legh even changes through the month with the cicle (yes, even if you're on the pill), but overall I wouldn't go crazy over lengh.
I imagine it is hard to be incredibly careful and never quite being able to let loose with your partner if you have a massive dick like that.